/*
 * insert_username.c
 * $Modified: Thu Oct 16 08:13:42 1997 by brook $
 * contrib/spi/insert_username.c
 *
 * insert user name in response to a trigger
 * usage:  insert_username (column_name)
 */
#include "postgres.h"
#include "knl/knl_variable.h"

#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "executor/spi.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/rel_gs.h"

PG_MODULE_MAGIC;

extern Datum insert_username(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(insert_username);

Datum insert_username(PG_FUNCTION_ARGS)
{
    TriggerData* trigdata = (TriggerData*)fcinfo->context;
    Trigger* trigger = NULL; /* to get trigger name */
    int nargs;               /* # of arguments */
    Datum newval;            /* new value of column */
    char** args;             /* arguments */
    char* relname = NULL;    /* triggered relation name */
    Relation rel;            /* triggered relation */
    HeapTuple rettuple = NULL;
    TupleDesc tupdesc; /* tuple description */
    int attnum;

    /* sanity checks from autoinc.c */
    if (!CALLED_AS_TRIGGER(fcinfo))
        /* internal error */
        elog(ERROR, "insert_username: not fired by trigger manager");
    if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "insert_username: must be fired for row");
    if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "insert_username: must be fired before event");

    if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
        rettuple = trigdata->tg_trigtuple;
    else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
        rettuple = trigdata->tg_newtuple;
    else
        /* internal error */
        elog(ERROR, "insert_username: cannot process DELETE events");

    rel = trigdata->tg_relation;
    relname = SPI_getrelname(rel);

    trigger = trigdata->tg_trigger;

    nargs = trigger->tgnargs;
    if (nargs != 1)
        /* internal error */
        elog(ERROR, "insert_username (%s): one argument was expected", relname);

    args = trigger->tgargs;
    tupdesc = rel->rd_att;

    attnum = SPI_fnumber(tupdesc, args[0]);

    if (attnum < 0)
        ereport(ERROR,
            (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION), errmsg("\"%s\" has no attribute \"%s\"", relname, args[0])));

    if (SPI_gettypeid(tupdesc, attnum) != TEXTOID)
        ereport(ERROR,
            (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
                errmsg("attribute \"%s\" of \"%s\" must be type TEXT", args[0], relname)));

    /* create fields containing name */
    newval = CStringGetTextDatum(GetUserNameFromId(GetUserId()));

    /* construct new tuple */
    rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, &newval, NULL);
    if (rettuple == NULL)
        /* internal error */
        elog(ERROR, "insert_username (\"%s\"): %d returned by SPI_modifytuple", relname, SPI_result);

    pfree(relname);

    return PointerGetDatum(rettuple);
}
